Clean Architecture

Practical layering, DIP enforcement, and anti-over-engineering — grounded in Robert C. Martin's Clean Architecture, SOLID (SRP/OCP/LSP/ISP/DIP), component principles (CCP/CRP/ADP/SDP/SAP), and Musk's five-step algorithm.

Router Rules

• Description-based routing: trigger on architecture-significant scenarios — four-layer decomposition, DIP violation, Repository/Adapter boundary design, technology evaluation, over-engineering detection.
• Once triggered, follow Workflow. This is an architecture governance entrypoint, not a debugging or code-review tool.
• Hard-exclusion list (answer directly, do NOT invoke): pure code quality, DDD, system design interviews, single-DTO micro-decisions, cache library selection, DI framework debugging, diagram drawing, translation, formatting.
• Stack-agnostic: explain in canonical four-layer terms (Entities / Use Cases / Interface Adapters / Frameworks & Drivers), then map to the user's actual framework (Express/Next.js/Go/Spring). Service/Repository/Controller are implementation-pattern mappings, not primary layer names. Adopt the user's existing conventions where established.
• Read-only audit requests: zero file modifications.

Use when

• Monolithic controller/route bloat → SRP decomposition + DIP-driven refactoring into four layers
• Entity/Use Case directly importing external SDK (Stripe/PayPal) or DB driver → Dependency Rule audit
• Technology evaluation: microservices / Kafka / Redis / caching → bounded-context fitness and CCP alignment
• Storage or API migration (MongoDB→PostgreSQL, REST→GraphQL) → Repository boundary design, Ports & Adapters impact
• Multi-vendor integration → Adapter layer design, swappability via interface contracts

Do NOT use when

• Diagramming, translation, formatting, title-writing, document summarization
• Framework debugging: DI wiring failures, HTTP 500, slow SQL, index optimization
• Micro-decisions: React component splitting, single DTO addition, naming
• System design interview problems (Twitter-scale, bit.ly, Saga pattern, multi-tenancy)
• User explicitly opts out ("don't talk about architecture," "just explain")

Workflow

1. Diagnose — probe before prescribe: Elicit scale, team size, concurrency, change frequency. CCP: same change reason + same change cadence → co-locate. SRP: different actors → separate. Invest boundaries only on proven variation axes (3+ historical changes at the same seam); YAGNI on unproven axes.
2. Principle evaluation: Assess against the four-layer concentric model + Dependency Rule (∀ dep → inward; Entities ⊥ Use Cases ⊥ Interface Adapters ⊥ Frameworks & Drivers), SOLID (SRP/OCP/LSP/ISP/DIP), component cohesion (REP/CCP/CRP) + coupling (ADP/SDP/SAP), Musk's five-step algorithm, and engineering dialectics (unity of opposites, quantitative→qualitative change, negation of negation). See Reference Map.
3. Structured answer (architecture scenario confirmed):
   • Four-layer map: Entities / Use Cases / Interface Adapters / Frameworks & Drivers — each layer named with contents
   • Dependency Rule: source-code dependencies point inward only — concrete direction arrows drawn
   • Stack mapping: canonical layers projected onto user's actual framework + directory structure
   • Code example: minimal before/after with layer labels, ≤ 50 lines
4. Anti-over-engineering gate: Every "adopt complex solution" recommendation must survive Musk's five steps — Question → Delete → Simplify → Accelerate → Automate, order invariant. Monolith suffices → do NOT propose microservices. Single implementation → do NOT propose interface abstraction.
5. Documentation isomorphism (as needed): Architecture decisions must persist as discoverable artifacts for downstream Agents and developers. Code change without documentation update = incomplete. Granularity matches impact radius: cross-layer refactor → L3→L2→L1 full loop; single import change → one L3 line. See Reference Map → Documentation Isomorphism.

Output Contract

• Hit: diagnosis + four-layer map + Dependency Rule explication + stack mapping + ≤50-line code example + anti-over-engineering verdict. Major architecture decisions → append L2/L3 documentation skeletons.
• Miss: answer directly; suppress this skill's template.
• Scaffold restraint: full directory scaffold (> 5 directories or named files) only on explicit request. Default: layer-level directory suggestions (≤ 5 directory names, no specific files).

Reference Map

• Theory & Principles: references/clean-architecture.md
• Anti-Over-Engineering: references/musk-algorithm.md
• Engineering Philosophy: references/engineering-philosophy.md
• Documentation Isomorphism: references/geb-fractal-docs.md